We are studying the propagation of action potentials in the heart of the tunicate Styela Plicata because of the simple, regular arrangement of the cardiac cells into a large thin walled tube which is a single cell layer thick. We plan to voltage clamp the heart cells to better understand the ionic basis of the action potential and then to use this experimental model along with computer simulations of two dimensional cable equations to study the propagation of action potentials through the sheet of cells.